Threaded abrasive wheel dresser



Sept. 27, 1949. LOHUTKQ 2,482,785

THREADED ABRASIVE WHEEL DRESSER Filed Dec. 4, 1946 2 Sheets-Sheet 1 IN VN TOR.

BY I y Sept. 27, 1949. F. A. LOHUTKO 2,482,785

THREADED ABRASIVE WHEEL DRESSER I Filed Dec. 4, 1946 2 Sheets-Sheet 2 ToRNEY- Patented Sept. .21, 1949 THREADED ABRASIVE WHEEL DRESSER,

Floryan A. Lohutko, Detroit, Mich,

mesne assignments, to

assignor, by Niles-Bement-Pond Company, West Hartford, 001111., a corporation of New Jersey Application December 4, 1946, Serial No. 714,027

4 Claims. (01. 125-11) This invention relates to the dressing of threaded abrasive wheels such as are adapted for the finish forming of gear teeth. A common method of forming such a thread on an abrasive wheel for such purposes is by means of crushing the thread into the periphery of the wheel as by means of a ribbed pressure roller suitably controlled to provide the necessary lead. After such a thread has been produced, it is desirable that the surfaces of the thread be finish dressed to provide the accurate cross sectional form of thread to eventually grind the required tooth form on a gear blank and also that the fianks of the thread be given a physical surface condition of such qualities that the eventual grinding will be of a high degree of excellence as to surface finish and fidelity as to tooth form.

In my present invention I propose to effect such finish dressing by means of a high speed wheel of a composition known as free-cutting material such as diamond-impregnated carboloy or similar material.

The invention also contemplates the mounting of such a dressing wheel in relationship to thread crushing means and under such control as to position and adjustment that it may be accurately given the pitch and lead of the crushed thread in performing its dressing operation.

Still further objects or advantages additional or subsidiary to the aforesaid Objects, or resulting from the construction or operation of the invention as it may be carried into effect, will become apparent as the said invention is hereinafter further disclosed.

In carrying the said invention into effect, I may utilize the novel arrangement of elements hereinafter described, by way of example, having reference to the accompanying drawing, wherein:

Figure 1 is a schematic elevation of a mechanism for the profiling of an abrasive gear grinding wheel by means of a crusher roll and its finish dressing by means of a high-speed freecutting disk, the precise proportions of the elements of the structure as shown being departed from or exaggerated for purposes of clear and simple illustration;

Figure 2 is an end elevation of the abrasive wheel and the dressing disk viewed from a plane indicated by the line 2-2 in Figure 1;

Figure 3 is a side elevation of the crusher roll and dressing disk together with their mountings; and

Figure 4 is a front elevation of the same.

Similar characters of reference indicate similar parts in the several figures of the drawing.

Referring first to Figure 1 of the drawings; It indicates an abrasive wheel, such as may be intended for the grinding or forming of 'teeth on a spur wheel blank, the said abrasive wheel being characterized by its having formed 'on its periphery a thread I l which is in cross-section conjugate to the rack form of the gear to be ground; and the present invention relates to the means for forming this thread on the periphery of the abrasive wheel.

For such purposes I utilize an annularly ribbed crushing roll l2 having a rib to rib spacing, which is equivalent to the circular pitch of the gear which the abrasive wheel is eventually intended to grind.

The abrasive wheel l0 and the crusher roll 12 areintended to have relatively reciprocal motion imparted thereto; and, in the present example, such reciprocation is confined to the abrasive wheel although as a matter of design it could be imparted to the crusher roll to produce the same result as will be well understood; and it is desired that throughout the present description and in interpreting the claims that the utilization of the terms reciprocating the abrasive wheel be considered in such broad sense as to embrace the obvious alternative of the reciprocation of the presure roll relative to the abrasive wheel.

The abrasive wheel Ill is shown as being mounted for rotation on and by the shaft I4 which is splined, as at l5, for longitudinal sliding connection with a driving coupling Hi, the latter being in turn driven by the bevel gear ll of a ther meshing bevel gear I9.

differential which includes pinions l8 and a fur- 20 is a driving motor, preferably of the variable speed type, operating a driving pinion 2| which meshes with ring gear 22 of the said differential, this ring gear also meshes with the first of a, train of change speed gears 23, 24, 25, 26 and 21. The said gear 2'! drives a feed screw 28 which is threaded into the arm 29 of a bracket 30 secured to the said shaft M. This bracket 30 is provided with suitably adjustable stops 3| and 32 positioned for the timed operation of a reversing switch 33 for effecting the reversing of the drive motor 20 as said switch is operated by one or another of said stops.

34 is a shaft through which rotation of the gear I of the differential may be effected from any suitable source, as by a belt 35, to control the speed of rotation of the shaft M- relative to that of the driving motor to meet special circumstances; but this is not an essential part of the 'present invention and need not be discussed in 3 any further detail herein. For the purposes of this description, the gear I8 may be considered as fixed.

It will be apparent that by means of the gearing described and the operation of the feed screw 28 thereby, the abrasive wheel I8 may be caused to reciprocate, say, to the extent indicated by the dotted lines in Figure 1, while it is at the same time being rotated and that, as this reciprocation is reyersed by tl e ape 'ation of the reversing switch 33 in the apparent manner, the direction of rotation of the abrasive wheel will at the same time be reversed; so that any stationary point presented-to the surface of the grinding wheel during such operation thereof will traverse a hellcal path thereon and retrace the same path in the opposite direction upon reversal of the motions described.

As a section of the threaded abrasive wheel taken on a plane at right angles to the lead of the thread is comparable in all its elements to a rack of the gear to be ground thereby, the cross-sectional form of the ribs of the crusher roll is accordingly a counterpart of such rack. Thus the crusher roll, when applied to the abrasive wheel in the manner illustrated with requisite feed-in adjustment toward the axis of the wheel and relative longitudinal feed, in the illustrated example, of the abrasive wheel to conform with the lead of the thread or threads to be formed thereon, will crush the thread form including the top of the thread, and also crush the root of the thread somewhat below the depth to which it is to be finally dressed.

The crusher roll is shown as being mounted for adjustment and operation on a fixture which includes a frame structure 38 carrying a slide 39 which is adjustable by means of a micrometer feed 4'0 toward and from the axis of the abrasive wheel III, the front end of the said slide being provided with a bracket H on which the said crusher roll I2 is mounted for free rotation. This bracket H is pivoted on the slide 39 at 42 so that it may be swung about an axis passing transversely through the axes of the crusher roll I2 and of the abrasive wheel Ill. The pivot 42 is also located so that its axis passes through one of the ribs of the said crusher roll I2 as clearly shown in Figure 4.

42' are looking screws for securing the bracket M in positions of angular adjustment about the axis of the pivot 42 in order that the said crusher roll I2 may be set with its ribs lying in planes conforming with the lead angle of the thread to be crushed on the periphery of the said abrasive wheel III.

A second slide 43 is mounted on the slide 39 and provided with a micrometer feed 44' for its adjustment, this slide 43 carrying the bracket 45 which is pivoted at 48. This bracket 45 is inverted in relation to the previously described crusher roll bracket 4I and carries the spindle 41 of a dresser disk 48, the peripheral portion of which disk is shaped in counterpart of the true form of the flanks of the thread to be form-finished on the said abrasive wheel Land is of a composition known in the art as freecutting (such as of a diamond-impregnated carboloy).

The said pivot 48 is also positioned so that its axis is projected through the periphery of the said disk 48 and through the axis thereof and is furthermore carried by a slide 4'8 provided with a micrometer feed 50 whereby the said pivot may be adjusted, relative to the pivot 42 of the crusher roll bracket, in order that the disk 48 may be accurately positioned to fall precisely between the threads, or the development of the threads. formed on the abrasive wheel III by the crusher roll. In other words, if the abrasive wheel ID be so positioned that its periphery spans both the crusher roll and the disk 48, they would then both accurately mesh with the thread of the abrasive wheel.

In order that the said disk 48 may be adjusted and set to the helix angle of the thread of the abrasive wheel, the bracket 45 is also capable of angular adjustment on the pivot 46 and may be locked in such positions of adjustment by locking screws 5|. on the said bracket 45 to drive the spindle 41 of the disk 48 as by means of the belt 53.

It will now be seen that, by setting the crusher roll I2 and the dresser disk 48 at the helix angle of the thread to be formed and finished on the abrasive wheel II), as in the manner clearly shown in Figure 3, and properly regulating the distance between the pivots 4'2 and 46 in the manner described, the thread may be first crushed into the periphery of the said abrasive wheel In (such as by employement of the means illustrated in Figure 1) and thereafter axial movement of the abrasive wheel continued until the disk 48 enters and follows the thread of the said wheel I0, whereupon the high-speed rotation of the freecutting disk will perform the thread finishing operation.

By using such a free-cutting disk in the manner described, a high degree of thread form may be secured without breaking down the surface structure of the thread and in a manner producing a surface grain structure having physical qualities which are highly desirable for the grinding functions which the said abrasive wheel is eventually intended to perform.

It will be understood that, where back lash in transmission is to be contended with, the dressing described may be effected in one longitudinal direction, the dressing tool being withdrawn from contact with the abrasive wheel during its reverse or return stroke such as by the manual means provided and described.

This invention may be developed within the scope of the following claims without departing from the essential features of the said invention, and it is desired that the specification and drawing be read as being merely illustrative of a practical embodiment of the same and not in a strictly limiting sense.

What I claim is:

1. The method of finish-forming a helically threaded abrasive wheel of the type described which comprises subjecting the fianks of the wheel thread first to the action of a crusher wheel conformed to the counterpart of the finish form of the abrasive wheel and thereafter to the progressive cutting action of a high-speed disk the axis of which is disposed obliquely to the axis of the abrasive wheel, said disk having a peripheral portion of free-cutting material and of a crosssection in counterpart of the finish form of the opposed flanks of the thread.

2. Means for finish-forming a helically threaded abrasive wheel of the type described, said means comprising a disk having a marginal portion of free-cutting material, adjustable means for supporting said disk in mesh with the abrasive wheel thread and in a plane conforming to the helix angle of said thread, means for rotating'said abrasive wheel at a relatively slow 52 is a motor also mounted speed, means for rotating said disk at a relatively high speed, and feed mechanism providing relative axial motion between said abrasive wheel and said disk in timed relation to each other whereby the disk will traverse the thread space of said abrasive wheel.

3. In a machine for forming a helical thread on the periphery of an abrasive wheel, in combination, a crusher roll, means effecting relative axial movement between said crusher roll and said abrasive wheel during rotation of said abrasive wheel whereby said roll will crush a thread formation into the periphery of said wheel, a high-speed disk having a marginal portion of free-cutting material positioned to enter and traverse the thread space of said wheel upon further relative axial motion of said wheel, and means effecting said further axial motion upon the completion of the initial crushing operation to provide the thread finishing operation by said disk.

4. In a machine for forming a helical thread on the periphery of an abrasive wheel, in combination, a crusher roll, means for adjusting the axis 6 of said roll to the angle of thread lead to be formed, means effecting relative axial movement between said crusher roll and said abrasive wheel during rotation of said abrasive wheel whereby said roll will crush a thread formation into the periphery of said wheel, a high-speed disk having a marginal portion of free-cutting material positioned to enter and traverse the thread space of said wheel upon further relative axial motion of said wheel, means effecting said further axial motion upon the completion of the initial crushing operation to provide the thread finishing operation by said disk, and means for adjusting the plane of said disk to the lead angle of the wheel thread.

FLORYAN A. LOHUTKO.

REFERENCES CITED The following references are of record in the 

